Diagnosis and management of traumatically induced hemicrania continua and neuropathic pain secondary to facial gun shot wound

Near fatal gunshot wound to the face results in lifesaving surgery and restorative procedures. Chronic pain followed. This is the probable first case report of posttraumatic hemicrania continua and its successful management.


| CLINIC AL E VALUATION
The orofacial pain evaluation included a detailed history, comprehensive clinical evaluation, judicious use of adjunctive diagnostic testing, formulation of a differential diagnosis and implementation of a treatment plan. The minimal information necessary for an adequate history includes, but is not limited to the chief complaint, a review of systems, past medical history, review of the location, duration, frequency, intensity, precipitating and ameliorating factors related to any pain complaint, current and past medications or treatments and efficacy of past treatment. The evaluation began with clinical observation.
In this case, the chief complaint of limited mandibular range of movement was obvious. However, careful observation found much more. In addition to the limited mandibular function and pain of the masticatory muscles, the patient reported a second complaint of headache with periorbital pain and a burning and tingling sensation along the left zygomatic arch. The left forehead was flat compared to the right with the left eyebrow much lower than on the right. The left eye appeared smaller than the right, and the eyelid was puffy, consistent with ptosis ( Figure 3A,B). Anisocoria was present with asymmetrical pupillary size; the left was somewhat smaller than the right. The left sclera was reddened with an injected appearance. During the interview, the patient was observed constantly wiping his left eye and left nostril, due to persistent rhinorrhoea and lacrimation. He was also observed turning away from the windows, shielding his left eye from the light. He described photophobia, explaining that he was 'coming down from an attack' .
These autonomic features associated with left-sided headache were consistent with Horner's Syndrome. Headache was constant with background discomfort waxing and waning throughout the day from levels of moderate discomfort, escalating to severe episodes that might occur at any time. Background discomfort was constant with occasional 'attacks' , exacerbations as described above. It was during these 'attacks' the patient experienced the associated autonomic features of lacrimation and rhinorrhoea. He said that since being shot, 'this has never left' . He denied prior symptoms of a similar nature and assumed that these symptoms were the residual effects of the trauma and nothing could be done.

| Summary of chief complaints
• Limited mandibular opening and masticatory musculoskeletal pain.
• Left half-head headache and periorbital pain associated with autonomic features.
• Facial nerve paralysis involving the forehead.
• Burning and tingling pain of the left zygomatic region.

F I G U R E 2
The left temporomandibular prosthesis is in place. The scatter of shrapnel throughout the area F I G U R E 1 A-P CBCT view of the entry wound. Note bullet trajectory and potential for trigeminal and facial nerve at the site of the exit wound

| D IFFERENTIAL D IAG NOS E S
Cluster headache (CH), chronic paroxysmal hemicrania (CPH) and HC often mimic anterior maxillary odontogenic pain leading to inappropriate dental procedures. Therefore, a differential diagnosis must also include odontalgia. Differential diagnoses also considered in this, and similar cases are temporomandibular disorders and  Table 1). Post-traumatic TAC is reported following a head injury. 3 The suggested mechanism for post-traumatic migraine is secondary to axonal injury or a shearing effect of the brainstem, even after mild or moderate injury. A physiological shift within the brainstem can lead to chronic migraine. 4 Similar posttraumatic physiological events are associated with the onset of SUNCT or SUNA, suggesting an abnormality in the brainstem or hypothalamus, or the activation of a pre-existing predisposition to such abnormality. 5 Another potential mechanism is the activation of trigeminovascular nociceptive pathways, which activates a trigemino-autonomic reflex resulting in headaches. 6 TACs are unilateral, considered side-locked, and associated with autonomic features ( Table 2). TACs have common features, with the exception of HC, in that they are typically episodic; HC is an uncommon, benign unilateral and continuous headache, with superimposed exacerbations of severe pain and autonomic features ( Table 3). Other features may include photophobia, phonophobia or both, nausea and ocular discomfort.   A single case series of traumatic HC has been reported. 14 However, the authors do not discuss the pathogenesis of traumatic HC. It was hypothesised that comminuted fractures of the maxilla may have resulted in HC with the following possible contributory pathophysiologic mechanisms or a combination of these mechanisms: • activation of the CN-V2 trigeminovascular system and disinhibition of trigeminal autonomic reflex with possible structural reorganisation in the CNS, • neuroinflammation and neuropraxic effects on the sphenopalatine ganglion, • considering the severity of the trauma, it is also plausible that there was additional activation of the hypothalamus through its connection with the trigeminal nuclei and trigemino-parasympathetic reflex. 21 Symptoms must be present for more than three months. 11,12

| MANAG EMENT
The HC was effectively treated with indomethacin. The patient was titrated from 25 mg per day up to 75 mg per day in divided doses.
After only several days he realised immediate relief from the HC and was titrated downward to the minimum effective dose of 25 mg daily.
Nortriptyline was prescribed, 10 mg daily at bedtime. He realised the remarkable and rapid diminution of PPTTN within one week ( Figure 4A-C).
He remained completely pain-free for two years at which point he felt breakthrough tingling in the area of the left zygomatic branch of CN-V 2, low-dose pregabalin, 75 mg three times daily, was added three years ago. The patient has been followed for more than six years and remains pain-free on this regimen. No treatment for the facial nerve injury was possible and considered permanent.
The mandibular range of motion was rehabilitated to 28 mm with physical therapy modalities including progressive gentle stretching home care exercises with hot and cold packs.
No treatment was possible for the facial nerve injury.
The patient is followed three times annually and routine serology is collected.

CO N FLI C T O F I NTE R E S T
The authors claim no conflict of interest or relationship, financial or otherwise that might be perceived as influencing an author's objectivity.

E TH I C S A PPROVA L
Patient consent for this publication has been given.

PE E R R E V I E W
The peer review history for this article is available at https://publo ns.com/publo n/10.1111/joor.13324.

DATA AVA I L A B I L I T Y S TAT E M E N T
As this is a case report, the manuscript does not contain any data to be shared.